Eating More Fish May Protect Your Brain Against Air Pollution

When you think about air pollution’s effect on your health, it’s probably your lungs you’re most worried about.

But studies show that exposure to the tiniest air pollutant particles — particles 30 times smaller than the width of a human hair, often carried in smoke or exhaust fumes — is linked to decreased brain volume and the risk of a faster decline in thinking and memory skills with age.

One such study, published in November 2020 in the journal Neurology, looked at women in their 70s and 80s who lived in high air pollution areas. The researchers, who took brain scans of the women at the beginning and end of the five-year study, found that breathing in these kinds of airborne particles was linked to shrinkage in the areas of the brain vulnerable to Alzheimer’s disease — the equivalent of a 24 percent increased risk of the disease over five years.

But another study suggests that at least one or two servings of fish weekly may counteract some of air pollution’s effects on the brain, according to research first published in July 2020 in the journal Neurology.

Researchers found that among older women in the United States who lived in areas with high levels of air pollution, those who had the highest blood levels of omega-3 fatty acids had significantly less brain shrinkage than women with the lowest levels. These healthy unsaturated acids are in fish, like salmon and tuna, and other seafood, as well as in nuts, seeds and plant oils.

Women with the highest omega-3 blood levels also had greater brain volume in the hippocampus, the region of the brain associated with memory.

“Our project is just one of many studies supporting that healthy lifestyle, including healthy diet, is a good strategy to slow down age-related cognitive decline,” study coauthor Ka Kahe, a professor of epidemiology and obstetrics and gynecology at Columbia University’s Irving Medical Center, told AARP in an email.

The findings suggest that “higher levels of omega-3 fatty acids in the blood from fish consumption may preserve brain volume as women age and possibly protect against the potential toxic effects of air pollution,” Kahe wrote in a press release.

One reason may be that omega-3 fatty acids have been shown to fight inflammation in aging brains and to reduce brain damage caused by neurotoxins like lead and mercury, Kahe explained.

In the study, researchers wanted to determine if omega-3s could protect against air pollution toxins.

The study involved 1,315 women, ages 65 to 80, who did not have dementia at the start of the three-year research period. The women filled out questionnaires about what they ate, their physical activity and their medical history.

The diet questionnaires asked specifically about how much fried versus non-fried fish each of the women consumed. Non-fried included baked or broiled fish, or dishes like tuna salad and non-fried shellfish. Fried fish was not included because research has found that frying, especially deep-frying, damages omega-3s.

The women had blood tests to determine their omega-3 levels and MRI scans to measure their brain white matter volume. White matter, which makes up half the brain, consists of nerve fibers and plays a role in important brain functions like learning and memory.

Researchers then used the women’s home addresses and federal environmental data to track their three-year average exposure to air pollution.

They found that the women with the highest blood levels of omega-3 fatty acids had “significantly greater” white matter volume in their brains, and that the neurotoxic effects of air pollution on brain volume were much smaller than in women with low levels of omega-3s.

The findings also indicated that only small servings of non-fried fish servings were necessary for these benefits — just one to two servings a week, Kahe says. The U.S. Dietary Guidelines call for 8 ounces of fish or seafood weekly, while the American Heart Association recommends two 3.5-ounce servings a week.

The study is only observational, he cautions, meaning it doesn’t establish a cause for the brain effects, only that there may be a relationship between eating fish and greater brain white matter volume despite air pollution.

What you should know:

• These fish contain the most omega-3 fatty acids. Many types of fish contain omega-3 oils, but fatty fish have the highest amounts. Aim for a couple of servings a week from this school of fish: salmon (farmed or wild), mackerel, tuna (canned or fresh), trout (farmed or wild), sardines and herring.
  
• More research links fish to brain health. A study by eye researchers at the National Institutes of Health, who were looking at diet’s effect on the brain and eye disease, found that high fish consumption was linked to the slowest rate of decline in memory and thinking skills in people followed for 10 years compared to those who ate the least fish. The study was published in April 2020 in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
  
• Learn more about fish and your brain. Watch this short video from Staying Sharp and physician John Whyte on why coldwater fish, with their high level of healthy oils, are the number one brain-friendly food.